After Bloch discussed the cases with Korach, the NIEHS researchers conducted experiments using human cells to determine if the oils mimic the effects of estrogen, the female hormone that stimulates breast tissue growth, or inhibited the effects of androgen, the hormone known to control masculine characteristics and inhibit the growth of breast tissue. The researchers tested the ability of the oils to modulate or inhibit gene expression.
"The results of our laboratory studies confirm that pure lavender and tea tree oils can mimic the actions of estrogens and inhibit the effects of androgens," said Korach. "This combinatorial activity makes them somewhat unique as endocrine disruptors."
Bloch said the laboratory studies support his hypothesis. "Since there was no identifiable cause for prepubertal gynecomastia in the three patients we reported, we speculated that environmental factors might be contributing to their condition. Together, the case histories and NIEHS in vitro studies provide support for our hypothesis that topical exposure to lavender and tea tree oils likely caused gynecomastia in the three patients."
The oils did not alter the levels of the usual forms of circulating estrogens and androgens in the boys. "We do not anticipate any long term effects on hormonal levels," said Derek Henley, Ph.D., the lead NIEHS author on the study. It is unknown whether the oils have similar endocrine disrupting effects in prepubertal girls, adolescents or adults.
"This study clearly demonstrates how clinical observations can be supported by basic science research," said NIEHS Director David A. Schwartz, M.D.
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Contact: Robin Mackar
rmackar@niehs.nih.gov
919-541-0073
NIH/National Institute of Environmental Health Sciences
31-Jan-2007